encapsulation

gistfile1.js

  function Rectangle(h,w) {
    var width=w; // Both the 'width' and 'w' is private
    var heigth=h; // Both the 'height' and 'h' is private
    this.setWidth= function(w){ width=w;}
    this.setHeight= function(h){ heigth=h;}
    this.getWidth= function(){ return width;}
    this.getHeight= function(){ return heigth;}
    this.constructor.prototype.getDiagonal=function() {
      return Math.sqrt(heigth*heigth+width*width);
    };
  }
  Rectangle.prototype.getArea=function() {
    // We must use accessors in a prototype kind of method,
    // then these methods can not access the private members
    // of a created object.
    return this.getWidth()*this.getHeight();
  };
  var rect = new Rectangle(60,70);
  rect.setHeight(20);